Does insurance companies have limits to their services such as maternity, etc.? My husband's adopted daughter keeps on going to the hospital for maternity care (miscarriages, etc.). Is there any limitations in a family plans' services? Is it individually

Read your contract. Each plan has its own limitations and or exclusions which are in written form in the contract.Many times these are also posted online or available to you by calling the customer service representatives at the company or the personnel office if you get your coverage through work.
You . You need to look at your particular plan. Health care reform has changed many policy limitations, exclusions and coverages. There are still some "grandfathered" plans as well as employer based "exempt" plans. Previously some plans paid out a lifetime maximum of say 1-2 million dollars in which case she may be utilizing some of the lifetime benefits. It has been rare for these limits to be used because of people changing jobs or changing insurance plans but it is good that you are thinking about these issues. Best place to start is in the insurance manual or booklet. If you don't have one ask for one from your employer or insurance agent. Good luck.